There is a need for an efficient catalytic process to manufacture ethers from linear monoolefins, thereby augmenting the supply of high-octane blending stock for gasoline. The C5+ lower molecular weight ethers, such as methyl sec-amyl ether, are in the gasoline boiling range. Lower molecular weight alcohols and ethers such as isopropyl alcohol (IPA) and diisopropyl ether (DIPE) are also in the gasoline boiling range and are known to have a high blending octane number. In addition, by-product propylene and butylenes are usually available in a fuels refinery. The petrochemicals industry also produces linear olefin streams in the C2 to C15 molecular weight range, and the conversion of such streams or fractions thereof to ethers can provide products useful as solvents and as blending stocks for fuel.
The catalytic hydration of olefins, particularly C.sub.3 olefin, to provide alcohols and ethers is a well-established art. Representative olefin hydration processes are disclosed in U.S. Pat. Nos. 2,262,913, 2,477,380, 2,797,247, 3,798,097, 2,805,260, 2,830,090, 2,861,045, 2,891,999, 3,006,970, 3,198,752, 3,810,848, 3,989,762, among others.
Olefin hydration employing medium pore and large pore zeolite catalyst is a known synthesis method. As disclosed in U.S. Pat. No. 4,214,107 (Chang et al.), incorporated herein by reference, lower olefins, in particular propylene, are catalytically hydrated over a crystalline aluminosilicate zeolite catalyst having a silica to alumina ratio of at least 12 and a Constraint Index of from 1 to 12, e.g., acidic ZSM-5 type zeolite, to provide the corresponding alcohol, essentially free of ether and hydrocarbon by-product. Acid resin catalysts such as "Amberlyst 15" may also be used for hydration of light olefins.
Recently, processes for the hydration of olefins to provide alcohols and ethers using zeolite catalyst such as ZSM-5 or zeolite Beta have been disclosed in U.S. Pat. Nos. 4,499,313 to Bell et al.; and U.S. Pat. Nos. 4,757,664, 4,857,664 and 4,906,187 to T. Huang. One of the advantages in using zeolite catalyst for hydration and/or etherification of light olefins is the regenerability of the catalyst. Where resin based catalysts can decompose at the high temperatures required to remove deactivating amounts of carbonaceous deposits, zeolite catalysts remain thermally stable and can be regenerated oxidatively or in contact with hydrogen.
According to U.S. Pat. No. 4,499,313, an olefin is hydrated to the corresponding alcohol in the presence of hydrogen-type mordenite or hydrogen-type zeolite Y each having a silica-alumina molar ratio of 20 to 500. The use of such a catalyst is said to result in higher yields of alcohol than olefin hydration processes which employ conventional solid acid catalysts. Use of the catalyst is said to offer the advantage over ion-exchange type olefin hydration catalysts of not being restricted by the hydration temperature.
European Patent Application 210,793 describes an olefin hydration process employing a medium pore zeolite as hydration catalyst. Specific catalysts mentioned are Theta-1, said to be preferred, ferrierite, ZSM-22, ZSM-23 and NU-10.
Formation of the initial carbon-oxygen bond in an alcohol by olefin hydration, such as the formation of isopropanol by hydration of propene, is a difficult step that puts severe demands on acid catalyst stability. These stability problems are due to hydrolysis of the active catalyst sites by liquid-phase water, and appear common to acidic resin, sulfuric acid, and zeolite catalysts.
It is known that medium pore, shape selective zeolite catalysts show a relatively low activity and reduced stability in propylene hydration processes. The role of water in contributing to the diminished activity of zeolite catalysts in propylene hydration is recognized. However, since water is a necessary reactant in the process, new methods to overcome the deleterious effects of water on catalyst while producing high IPA selectivity and catalyst activity have eluded discovery.
It is an objective of the present invention to provide a process for the production of isopropanol from propylene with high selectivity and catalyst life.
It is a further object of the present invention to provide a process for the production of IPA using medium pore, shape selective metallosilicate catalyst under conditions wherein catalyst activity is enhanced and catalyst productivity improved.
Yet a further objective of the present invention is to provide a process for the production of IPA using acidic zeolite catalysts such as ZSM-5, ZSM-23, ZSM-35 and Ferrierite under conditions of high catalyst activity, selectivity and stability.